Television system



Sept' 5, 1950 J. H. HoMRxGHous 2,521,009

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Sept. 5, 1950 J. H. HOMRIGHoUs 2521,009

TELEvIsIoN SYSTEM Original Filed Feb. 24, 1943 4 Sheets-Sheet 2 FIG. 2

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TELEVISION SYSTEM Original Filed Feb. 24, `1943 4 Sheets-Sheet 3 I I I 11 I l I |s4 I 154 I I Q I 153 I 2l8" P458 I |51 F I 2|7 I. I I 2:5../22' 'la/'2 l- 201 ala aoa zu am `-,z|o 2'6 209 3:?- I. L' .1

zNVENToR.

Patentecl Sept. 5, 1950 Fries TELEVISIION SYSTEM John H. Homrighous, OakPark, Ill.

Original application February 24, 1943, Serial No. 476,897. Divided andthis application October 9, 1945, Serial No. 1621,25'0

claims. (ol. 178-463) My invention relates to improvements in televisioncommunication systems.

(Jne of the main objects of my invention is an improved method. forsynchronizing the scanning devices and other mechanisms used intelevision.

Another object of my invention is an improved means for developingsynchronizing signals duringthe interval between scanned lines in afield and between the picture fields for Controlling the scanning actionat the transmitter and to modulate the carrier with the developedsynchronizing signals during the interval between scanned lines andpicture fields to thereby govern the scanning action at the receivingstation.

Another object of my invention is to provide an improved method forControlling interlace scanning.

Another object of my invention is to provide improved modulatingcontrols for transmitting video and sound signals alternately on thesame carrier.

Another object of my invention is the provision of means forautomatically governing the velocity of deflection.

Several methods for developing and transmitting control frequencies havebeen devised; for instance, control frequencies have been developedby-tuned circuits and transmitted separately from the video frequencieseither as a separate modulation on a separate carrier, or in theinterval between successive picture Vfields. In my prior application,Patent No. 2,309,393 of January 26, 1943, control signals are combinedwith the picture signals in such manner, that both are transmitted andreproduced as picture or vicleo signals; and in my prior applicationSerial No. 451,722 filed July 21, 1942, now Patent No. 2,398,- 641,issued April 16, 1946, single impulses or control signals are developedat the end of each line and at the end of each picture field, and thesesignals are modulated on the carrier during the interval between linesand the interval between picture fields to control the horizontal andVertical scanning action at the receiving station.

In my present invention, I employ similar means to that shown in myprior application Serial No. 451,722 for developing control pulses for'triggering or stopping the horizontal and vertical defiection of thecathode ray.

This synchronizing system may be known as the follow up system? that is,the receiving station is not driven into synchronism but follows thehorisontal and vertical movements of the transmitting station. Also,since no tuned circuits are used in developing the synchronizing signalsthis system is very flexible and will respend to any number of lines perpicture and also to the present television standard of thirtypicturesper second as well as to twentyf-four pictures per second' formotion picture film.

In my prior application Serial No. 451,722, l develop interlace scanningby causing the cathode ray in the first horizontal line in alternatefields to be returned from its mid-location to' its starting'point. Inmy present invention I pro.- vide an improved method for accomplishing'the same result.

Figures 1 and 5 are simplified diagrammatic views of a televisiontransmitting station, and a television receiving station, respectively,illusitrating the principles applied in this invention.

Figures 2 and 4 are circuit diagrams of the horizontal and verticaldeflecting apparatus re;- spectively, shown in Figure 1.

Figure 3 is a graphical view showing horizontal and verticalsynchronizing impulses.

Figure 6 is a circuit diagrarn of the horizontal and vertical deflectingapparatus illustrated in Figure 5.

Figures 'i and 8 are diagrammatic views of the arrangement of picturetubes projecting motion pictures to several Screens simultaneously.

In Figure l, the numeral i designates a cathode ray transmitting tube ofconventional type and is known as an "Iconoscope or it may be a tubedeveloped for perpendicular scanning of all points on the mosaio, and asillustrated it comprises a mosaic 2,' photoelectric screen on which alight image of the object is projected and an electron gun forgenerating a ray of electrons directed at the screen, and two sets ofdeflecting plates for defiecting the electron ray at the line and fieldfrequencies, so that it is caused to scan the screen. The picture isthereby developed and fed by -an output connector 3 to a modulatingamplifier A.

A carrier wave is provided by an oscillator 5. In the power amplifier tthis carrier wave is modulated by the frequency bank video or picturesignals and also by synchronizing impulses from' the horizontaldeflecting apparatus 1 and the vertical defiecting apparatus 8 betweenthe horizontal lines and between the image fields through the modulationamplifier 4. The signals from the amplifier f are supplied by aconnection' 9 to the antenna lil. The oscillator 5 may be controlled bya frequency stabilizing unit I I.

The control or synchronizing signals and the video signals aretransmitted on the same carrier. Sound signals may be transmitted on aseparate 3 carrier, or the signals from the microphone E2 after suitableamplification at lt may be modulated on the same carrier as the videosignals between the picture signals and the control signals for eachhorizontal line.

The image may be Iprojected onto the mosaic screen 2 directly from ascene, or the image may be projected onto the mosaic from a moving filmE4 disposed as shown, which is given intermittent movement by suitablemechanism to project each picture frame separately.

With reference to Figure 2, the apparatus 'E for horizontal defiectioncomprises a condenser I charged through an adjustable resistance Elifrom a source of positive voltage as indicated. By movement of theSwitches E02 and N33 another condenser EM may be charged throughresistance E05 from a source of high voltage to supply a different linefrequency for horizontal defiection. Charging current control may alsobe obtained by varying the resistances through movable contacts E05 andll to give close frequency adjustm-ents. Further line frequencyvariations may be obtained by providing other resistances and condensersconnected to the vacant switch contacts.

When the condenser E or Eili becomes charged, depending upon whichswitch contacts are closed, the saw tooth voltage wave in the platecircuit of tube E118 is impressed on the grid N39 of multiunit tube EE'through an adjustable contact E IE on the voltage dividing resistance 2which contact is for controlling or adjusting the amplitude of the sawtooth voltage wave. The output of the push-pull amplifier I Es suppliedto the load resistors EE3 and Elli will change the potential on thehorizontal deflecting plates 5 and I E6 of tube E to effect in a wellknown manner the forward movement of the cathode ray. In order toincrease the glow from the different degrees of shading in the images onfilm l, light rays from a source of light '5E may be directed toward thefilm which momentarily increases the brilliancy of the Various shadingsor intensifies the glow.

To initiate the discharge of the condenser l or IM I provide anauxiliary scanning device or a cathode ray tube E El of conventionaltype similar to tube l except that it may be of smaller size and it maycomprise a fluorescent screen EE8 of rectangular shape, and an electrongun for developing a ray of electrons directed toward the screen. Thecontrol electrode of this tube is biased to produce a constant intensityelectron ray. Two sets of electrostatic plates may be furnished, one set9 and E to control the defiection of the electrcn ray lengthwise thescreen, and another'set E2E and E22 to control the defiection of theelectron ray in a direction perpendicular to the length of the screen.Three photoelectric cells in separate evacuated bulbs are providedinside the cathode ray tube E ll. One photocell E23 extends across thetube near one edge of the screen and another photocell E2i is -placednear the center of the screen. The glass evacuated bulbs of thesephotocells may be coated with luminescent material similar to the screenin the cathode ray tube except that the coating on the photocells mayhave a shorter persistence tim'e.

The defiecting plates l E9 and E20 are connected in parallel to thedefiecting plates IE5 and HB of tube E 'so that the cathode ray in bothtubes travels across their respective screens in synchronism.

When the cathode ray tube l E7 arrives at the edge of the screen havingthe photocell 123,

the change of light in the photocell, due to the electron ray impingingthe fluorescent material on the outside of the photocell causes avoltage impulse to be applied to the grid E25 of the double triode tubeE2. The voltage change on the grid of tube E26 causes several things tohappen: first, the signal after amplification in the anode circuit isapplied to the control grid E27 of tube E through condenser E28 andresistance E29 toextinguish or lower the intensity of the electron rayduring its backward movement or retrace period; second, this signal isapplied through resistances l3ll to grid E 3! of tube E08 and afteramplification in the anode circuit it is applied through the couplingcondenser E32 and resistance E33 to the grid of the modulating videoamplifier 13 for modulating the carrier with a high amplitude impulseduring the backward movement of the electron ray or the retrace periodas illustrated at l3ll, Figure 3, to thereby control horizontaldefiection at the receiving stations; third, this signal is also appliedto the secondrgrid l35 of tube l2e` and after amplification in its anodecircuit it is then applied through resistance E36 to the grid E31 of thetrigger tube E08. This tube then becomes conductive to discharge eitherof the connected condensers lim or E04.

From the foregoing it Will be understood that the photocell E23initiates the cut off or horizontal return trace of the cathode ray,modulates the carrier with a high amplitude signal wave betweenhorizontal lines, and also reduces the intensity of the electron ray intube E. Furthermore, line frequency may be varied to meet any operatingcondition through the adjustment of the variable resistances iel and E05and the condensers E and iii/3, The amplitude or width of the patternscanned may be adjusted by the movable contact EH.

With reference to Figure Li, the vertical defiecting apparatus 3 isquite similar to the horizontal defiecting apparatus l and comprises acondenser ISS charged through an adjustable resistance E39 from a sourceof positive voltage as indicated. By rotating the Switches E43 and Mianother condenser M2 may be charged through the resistance M3 from thesource of high voltage to supply different predetermined frame orpicture frequencies. Charging current control may also be obtained byvarying the resistances E39 and M3 through the movable contacts E411 andE45, to give close frame frequency adjustments.

When the capacitances E38 or M2 become charged depending upon whichcontacts are closed, the saw tooth voltage wave in the anode circuit oftube E136 is impressed on the grid 147 of the double unit tube M8through an adjustable contact E on the voltage dividing resistance E50which contact is for Controlling or adjusting the amplitude of the sawtooth voltage wave. The output of the push pull amplifier tube M8supplied to the load resistances E49 and l5ll will change the potentialvia conductors E5! and E52 on the vertical deflecting plates and 152' oftube E to effect the forward movement of the electron ray.

To initiate the discharge of condenser E38 or E2 I provide an auxiliaryvertical scanning device or cathode ray tube l53 of conventional typeand similar to tube l'l previously described, except that it has twophotocells E54 and E55 in separate evacuated bulbs extending'inside ofthe tube E53 and near the cathode ray leaving edge of the screen E55.

The plates |5E and E52' are connected in paralaserooe l'el to thedefiecting platesl l'51 and l581respectively in tube [53, so that themovement of the electron ray across their respective screens will be insynchronism.

When thev electron ray of tube 153 arrives at the edge of the screenhaving the photocell IS', the change in intensity of light to the cellcaused by the electron ray i-mpinging the fiuorescent material on theoutside of the photocell bulb will cause a voltage impulse to be appliedto the grid [59 o-f the double triode tube l. The voltage change on thegrid of tube Hifi initiates three conditions: first, the signal afteramplification in the plate circuit is applied.- through resistance Il tothe grids 162 and 163 of' the double triode |64 after suitableamplification the signal is supplied from anode i'55 to couplingcondenser 166, conductor l'i, resistance Hil' to the grid of modulationampl-ifier 4 for modulating the carrier with a high amplitude impulsebetween picture fields or during vertical retrace. The second conditionis as follows: the signal amplified in the second plate circuit of tubelfl is appliedthrough coupling condenser 53, conductor 168' to the gridof tube IEG in the horizontaldeflecting apparatus 'I to cause, aspreviously explained, the return of the electron ray to its horizontalstarting position, lowering the intensity of the electron ray, andmodulating the carrier with a high amplitude signal in synchronism withthe modulating signal from the tube !64. The modulation of the carrierwith two signals of large amplitude in synchronism will produce a signalhaving an amplitude greater than either of the signals alone, asillustrated at E69, Figure 3. The third condition is as follows: thesignal on grid lg after amplification is also applied to the grid HO oftube |-6 and after suitable amplification in its anode circuit it isapplied. through resistance I'H to the grid ofV the trigger tube M6.This tube then becomes conductive to discharge either of the condensers4.38 or M2.

When certain types of camera tubes are used such as illustrated inFigure 1 it may be necessary to make corrections in the horizontal linedefiection for the Keystone"' effect and in order to do this I provide apush-pull amplifier screen grid tube 2, Figure 2, having a control gridI'I3 con'- nected in parallel toV the'grid lil!! of the amplifier HQ.ductor. ll' to the load resistor M9 to gradually vary the tube output inaccordance with the field defiection. The output of the push-pullamplifier l'i2 supplied to load resistances |16 and I'H Will now changethe potential on the horizontal defiecting plates H and i iii throughthe Switches HB and [-79 to correctfor unequal amplitudes for horizontalscanning when a pick up tube having its image plate inclined to thescanning beam is used at the transmitter.

Fromr the foregoing it will be understood that the photocell Iflinitiates the return of the electron ray both vertically andhorizontally to its starting point between fields, modulates the carrierwith a high amplitude pulse between fields or picture frames, and alsolowers the intensity of the electron ray between fields, simultaneouslyduring the retrace period'. Furthermore, line and frame frequency may bevaried to meet any operating condition such as twenty-four or thirtypictures per second. By observing the sweep or otherwise timing thecathode ray in tube |53 it may be adjusted through. the variableresistances land 143 and the condensers l38 and M2 to The screen gridI'M is connected by a con- 6 operate at' a particular' frequency While.the and-B' plitude may be adjusted' by'the movable. contact M9 to givethe desired height scanned on the mosaic or to cut olf'the verticaldeflection at any desired number of lines per field.

To provide interlace scanning, where the lines of one field fall inbetween the lines of the previous field, some means for delaying thelinescanningr in altern-ate fields must be provided-since the field retracecontrol pulse also returns the horizontal movement of the cathode ray toits starting point which will cause the electron ra-y to traveli inalmost a vertical direction during retrace instead of backwardrandforward acrosstheimage screen.

In order to accomplish the above method of interlace, where thev numberof lines per frame, and the number of frames per second may be varied asdesired, I employ apparatus to'defiect momentarilythe electron ray inltheV scanning control devices for exciting other photoelectric cells inthe scanning devices to thereby control the horizontal defiecti'on sothat theV firstl line in alternate fields Will only be onehalffthel'ength of the other scanned lines, which will have the effectof moving the electron ray in thecamera tube Vertically in alternatefields a distance of one half of the spacev between lines.

With further reference to Figure 4, to control interlace scanning, avoltage pulse is developed each time that the photocell I51lV is excitedto initiate the return of the electron ray to its start'- ing point inthe second anode circuit of tube I-GO', and applied through the switch I80, conductor l'8l, condenser M2; to the grid N33` of tulbe HM, Figure2. This positive pulse on the grid of' tube l8 4` allows current to flowthrough resistance momentarily to charge the condenser l8. This causes avoltage change in the plate circuit of tube 181 whichV is impressed onthe grid |88 of the double triode tube 189. The'output` from theamplifier tube l'89 is supplied to the load resistors |99 and 200 toalter the potential on the deflecting plates lZl and |`22 of thescanning control tube or device ||1 to deflect the electron ray in adirection perpendicular to the length of the screen. This smalldeflection of the cathode ray in tube IHV will only be for a short time,since the cathode ray during its first horizontal movement aftervertical retrace will impinge the fluorescence coating on the photocellIM located approximately in the middle of the screen but normally out ofthev path of the cathode ray. The change of light in this photoelectriccell causes a voltage impulse to be applied to the grid 20! of thedouble triode amplifier 2fll2. The volttage change on the grid of tube202 causes several things to happen: first, the signal or voltageimpulse after amplification in the second anode circuit is appliedthrough couplingl condenser'204, conductor N58' to the grid l25 of tube[26 thus causing the cathode ray of tube l and 1 to return to theirstarting points as previously described but, after only one half` of thedistance of a horizontal line was scanned, which will have the effect oflocating successive scanned lines in between the scanned line locationsof the previous field; third, the signal or irnpulse from the secondanode circuit of tube m2 is also applied over conductor 2%5, throughswitch 295' and coupling condenser 206 to the grid 201 of tube 208. Thispositive pulse-on the gridof tube 2ii8 allows current to flow throughresistance 209 momentarily to charge the condenser 2m, thiscauses avoltage change in the plate circuit of tulbe 2i| which is appliedthrough blocking condenseri-Z to the gridf'2l3 of the double amplifiertube 2 I'4. The-output from the amplifier tube 2|4 is supplied to theload resistances 2 i 5 and 2 I 5 to change the potential on thedeflecting plates 2|`| and 2 |8 of the scanning, control tube of device|53 to deflect the electron ray in a direction perpendicular to thelength of the screen. This defiection of 'the cathode ray will cause itto impinge the fiuorescent coating on the photocell l55 instead of thephotocell IS!! at the end of the vertical defiection. The change oflight in the photocell l55 causes a voltage impulse to beV applied tothe grid 2i49 of the double triode amplifier 220. The voltage change onthe grid of tube 220` causes several things to happen: first, the signalor voltage impulse after amplification in the anode circuits is appliedto the grid of the trigger tube 2|| through the blocking condenser 221.This tube then becomes conductive to discharge'the condenser 2m thusrestoring the cathode ray in tube |53 to its normal position; second thesignal is applied through coupling condenser 222 to the grid of triggertube 145 and also the signal is applied through coupling condenser 223-to the grid 162 of tube Iii-'l thus causing the cathode ray in tubes Iand 153 to return to their starting points as previously described.

Y From the above description 'it is shown that the scanning cycleV will`geep repeating, that is, the cathode ray in the vertical scanningcontrol device 153 will alternately excite the photocell i 54 and 155 tocause vertical retrace etc. and each time that the photocell lfl isexcited it causes the photocell IZ in the line control device l I'l,Figure 2, to become excited, thereby causing the line locations scannedon the image plate in alternate fields to fall in 'between the linelocations scanned in the intervening fields. The Switches |8ii and 2115'would be opened for progressive scanning.

Sound signals may be transmitted on a separate carrier; however, Iprefer to modulate the sound signals on the same carrier with the videosignals but each having a separate period of time. In order toaccomplish this the scene may be focused toward one side of the imageplate leaving a small narrow space for sound at the cathode ray, leavingedge of the image plate or mosaio, as illustrated at E39, Figure 3. Thisrequires some means of automatically stopping or cutting ofi modulationof the video signalsl before the cathode ray reaches the edge of theimage plate and at the same instant to start modulating the carrier bysound signals. To effect the change from modulating the carrier withvideo signals to modulating the carrier with sound signals or vice versaI employ a third photoelectric cell 249 located in the cathode rayscanning device Hi so that the cathode ray will impinge its outerCoating of luminescent material once for each horizontal line for ashort period of time before impinging the photocell |23. This causes anincrease of intensity of light in the photocell 240, thereby increasingthe potential on the grid 2t! of the tube 2:22 causing a voltage drop inthe load resistance 223 which is applied through condenser Eee andresistancei and conductor 2% to the control grid E21 of the cathode raypick up tube l to extinguish or lower the intensity of its cathode raywhereby video signals will not be developed during the interval ofincreased light in the photocell Z. The voltage drop in the loadresistance 2% is also applied to the grid l' of the tube 2d through the.condenser 2:39: and resistance 2533.

sne tube se is biased so that normally current will'flow through itsloadjresistanoe 25i pro-' ducing a'large voltage drop; This low voltageis applied to the screen-grid 252 of amplifying tube 253. The normal lowpositive voltage applied to the grid 252 is considerably below thepositive voltage applied through load resistance 254 to theanode and isof such value that it normally nullifies the conductivity of the tube253 during the period that the video signals are being modulated on thecarrier. However, the negative pulse applied to the grid 24] of tube 243is of suficient value to stop the fiow of current through the tube,thereby increasing the potential on the screen grid 252 whereupon themicrophone |2 or photocell 45 may vary' the potential on the controlgrid 255 to vary the output of tube 253 in accordance with soundvibrations. The variable output voltage is applied through condenser 255and resistance 25'ig and conductor 258 to the input circuit ofmodulation amplifier ii to modulate the carrier with sound signalsbetween the video signals and the synchronizing pulses. Therefore, videoand sound signals are modulated on the same carrier at differentintervals.

With reference to Figure 5, showing a receiving station, the antenna 2G!receives the carrier signals from the transmitter antenna ie to a radiofrequency amplifier 252. An oscillator 233 reacts with these signals inthe first detector stage 254 on the superheterodyne principle to producean intermediate frequency which is supplied to the video intermediatefrequency stage 265. After suitable amplication the video signals andthe control signals are detected at Zbt` and applied. to the poweramplifier 2t? and after amplification in this tube they are applied tothe picture tube or scanning device 28. The device 253 is represented asbeing in the form of a cathode ray tube of a conventional type andcomprises a fiuorescent screen 269, an electron gun for developing a rayof electrons directed at the screen, and two sets of electrostaticplates for defiecting the electron ray at the line and field frequenciesto cause it to scan the screen. The video signals are applied to thecontrol electrode of the electron gun, whereby, the intensity of theelectron ray is made to vary with the video or 'picture signals. Thehorizontal defiecting apparatus 21%] receives the line synchronizingimpulses from the second detector output, and the vertical defiectingapparatus 27| likewise receives its control signals fromthe output ofthe second detector.

The images from the screen 259 may be impressed on a luminescent coatedfilm or rotating member 272 disposed as shown which maybe given anintermittent movement by suitable mechanism in front of a suitable lampto project each picture separately.

Sound signals may be transmitted on a separate carrier or they may betransmitted as part of the video signals as shown in my priorapplication mentioned above. In my present invention the sound signalsmay be transmitted on the same carrier as the video signals but duringan interval between the picture signals and the control or synchronizingsignals. A photoelectric cell 2,13 preferably placed on the inside ofthe cathode ray tube arranged at one side of the tube and having acoating of luminescent material with a rather fast decay period, so thatthe sound signals at the end of each horizontal line will cause variousdegrees of light intensities in the photooell 213 to vary its signalcurrent output. These variations in signals efter am'plinra-4 9 tion at214 are reproduced as sound at the speaker 215.

With reference to Figure 6, the defiecti-ng apparatus 213 and 21-1 arevery similar to that described for the transmitter. The apparatus 216for horizontal deflecticn at the receiver, comprises a condenser 212charged through a variable resistance 211 from a positive source ofpotential as indicated. By adjusting the switches 21.8 and 219 othercondensers such as 283 may be charged through other resistances such as28| from a source of high potential to supply different line frequenciesfor horizontal defiection. Charging current control may be `o'btai'nedby varying the resistance through movable contacts 282 and 283 to giveclose frequency adjustments.

When the voltage across condenser 216 gradually increases or thecondenser 283 depending upon which switch contacts are closed, the sawtooth voltage wave iny the plate circuit of tube 28!! is impressed onthe grid 285 of the double purpose tube 285 through a -voltage| dividingresistance 281 and the adjustable contact 258 for Controlling the-amplitude of the saw tooth voltage Waves. The output of the doublepurpose amplifying tube 286 is applied to the-load resistances 289 and293 to change the potential on the horizontal deflecting plates 291 and292 of tube 268 to effect the forward movement of the cathode ray.

To initiate the discharge of condensers 21t or 280 inthe absence ofsignal l'. provide an oif and on" electron relay tube 293. This tube hasbeen described in my prior application Serial No. 472,105, filed January12, 1943, now Patent No.

14137.027, granted March 2,, 1948. The tube 232 may comprise acontrolelectrode 294 for deflecting the electrons to and from the anode 295.

When the voltage at the load resistance 2313 is increasing the potentialc-n control electrode 2,94 will also increase until its potential isapproximately the same as the potential of the anode 295. This willcause the electrons to flow from the cathode 295 to the anode 295 thuslowering the potential at the load resistance 291 which is appliedthrough condenser 298 to the grid 2.99 of tube 3532. This change inpotential after amplification in tube 323 is applied to the grid 32,! oftrigger tube 284. This tube then becomes conductive to discharge thecondenser 213 returning the electron ray in tube 258 to its linestarting position. Discharging the condenser 215 also decreases thepotential at load resistance 293 thus lowering the potential of thecontrol electrode 291! thereby causing the defiection of the electronsfrom the anode 295.

With further reference to Figure 6, the vertical defiecting apparatus21] is similar to the horizontal 'deflecting apparatus 212, andcomprises a condenser 322 charged through a variable resistance 303 froma source of positive potential as indicated. By retating the Switches394 and 325 another condenser 39,3 may be charged through a resistance301 from the source of positive potential to thereby supply differentframe or picture frequencies. Charging current control may also beobtained by varying the resistances through the movable contacts 328 andto give close frame frequency adi'ustinents.

When the voltage across the condenser 322 increases the saw tooth Wavein the plate circuit of tube Slli is impressed on the grid 3t! of tube 3i 2 through the resistance 213 and the adjustable contact Bl forcontrolling the amplitude of the vertical saw tooth wave. The output ofdouble purpose amplifier tube 3| 2 is applied to the load resistances3l5 and 3IG to increase and decrease the potential on the verticaldeflecting plates 3l1 and 318 of tube 238 to effect the verticalmovement of the electron ray,

To initiate the discharge of the condensers 302 or Bli-ii in the absenceof control signals I provide an oif and on relay tube 3 i 9 similar totube 293 which may ccmprise a control electrode 323 for defiecting theelectrons to and from the anode 321.

When the voltage at the load resistance 3l'6 is increasing the potentialon the control electrode 325 will also increase -until its potential isapproximately equal to the potential on the anode. This will cause theelectrons to flow from the cathode 322 to the anode .-32l thus loweringthe potential at the load resistance 322' momentarily which is appliedthrough the condenser 323 to the grid 321% of tube 325. This impulseafter amplification in tube 3215 is applied to the grid 326 of thetrigger tube 315. This tube then becomes conductive to dischargecondenser 32.2, returning the electron ray in tube 228 to its framestart position. Discharging the condenser 302 also decreases thepotential at load resistance 3|3 thus lowering the potential of thecontrol electrode 329 thereby causing the deflection of the electronsfrom the anode 32 l.

From the foregoing it will be understood that in the -absence ofsignals, due to f-ading, or in turning the receiver on when there is notransmitter operating, that the electron ray in the tube 2.68 willoscillate both horizontally and vertically.

The video and control signals are demodulated at the second ydetector orrectifyi-ng tube 2.66. These signals are applied to' the power amplifier261 and after suitable amplification they are impressed 'on the controlgrid of vthe picture tube 258. Since the control or synchronizingsignals are of a greater amplitude than the picture signals and appearat the end of each line and vat the end of each field, they may be vusedto blank or reduce the intensity of the cathode ray in the viewing tubeduring the retrace period.

The control signals from detector tube 266 are also applied to the gridsof tubes 321 and 32-8. The tube 321 for Controlling thehorizontaldeflection period is biased so that the picture Vsignals willnot produce anode current, but it does respond to both the line andfield synchronizing pulses to thereby apply a voltage impulse throughthe coupling condenser 323 to the grid '299 of tube 322. After suitableamplification in its anode circuit the signal is applied to the grid 3U|of the trigger tube 22!! to cause the discharge of condenser 21% therebyreturning the electron ray of tube 263 to its starting point.

The tube 328 biased to eliminate both the picture and the horisontalsynchronizi-ng impulses, but it will respond to the high amplitudesynchronizing pulses to impress a potential impulse through the couplingcondenser 333 to the grid fif; of tube 325. This tube will function aspreviously described to discharge the condenser thereby returning thecathode ray in tube to the starting point of the next field.

From the foregoing it is to be understood that the cathode ray in thereceiving tube will be returned to either its horisontal line startingpoint or the starting point of the next field from any location on thescreen upon the reception of a control or synchronizing signal. In otherwords, the horizontal control signals Will return the electron beam tothe starting point for the next line, and the Vertical control signalwill return 'resistance 3:3 l.

asarooe ll the electron ray to the starting point of the first line inthe next succeeding field.

The amplitude for the horizontal and vertical defiection is adjusted bythe movable contacts 282 and'3El8V to adjust the sweep of the cathoderay across the fiuorescent screen 269. The voltage on the anodes 295and321 may be adjusted to give considerable voltage drop in the loadresistances 297 and 322' when the cathode `ray reaches the leaving sideof the screen 259 or when it reaches its limit of travel due totheamplitude adjustment.

-The operation of the receiver is as follows: when the receiver isenergized, upon closing the power supply circuit the cathode ray willoscillate or travel forward and backward horizontally and vertically bydefiecting potentials developed bycharging the condensers 21% and 382and discharging these condensers by the cutl off devices or tubes 293and 319. However, upon the reception of synchronizing signals,interposed between lines and between picture fields, the line deflectngapparatus will function upon the reception of the horizontal controlpulse to return the cath-- ode ray to start the next line in synchronismwith the transmitter. Upon the reception of the firs't vertical controlpulse the vertical defiecting apparatus will operate to return theelectron ray to start the first line of 'the next succeeding field.'I'herefore the receiver will be automatically synchronized with thetransmitter upon the reception of 4the first verticalrsynchronizingiinpulse, and the line deflection will be in step with the transmitterupon the receptiii of the first horizontal control impulse.

'Synchronism is accomplished by transmitting a control signal duringVeach retrace period of the cathode 'ray in the pick up tube andutilizing this control signal at the receiver to return the cathoderayin the viewing tube to its starting point for the 'next' forwardmovement. In order to automatically control or regulate the scanningfrequencies at the receiver and to care for slight irregularitiesin thetransmitted control signals I employ a regulator comprising a glow lamp33i, a photo'cell 332, and a double purpose tube 333. The glow lamp 33land photoelectric cell 332 may be mounted in separate light- 'proofcontainers arranged in such a manner that the light from the 'glow lampwill be directed toward the photocell as indicated by the dotted line324.H

The operation of the regulator is as follows: as the voltage at theload-resistance '2% is increasing to move the electron rayhorizontallyforward, this increasing potential is ralso applied through condenser335 to the grid 335 of the glow lamp 331; This will gradually increasetheV current through the glow lamp to cause it to glow more brilliantly.The variable light intensitiesfrom the glow lamp 33! are directed towardthe photocell 332 as previously explained, and as the brilliancyincreases the potential on the grid 331 is increased. The grid 333' isbiased so that current will only iiow in its plate circuit during thehigh amplitude of the saw tooth voltage wave or for a small distance oftravel of the electron ray at the leaving edge of the screen. Thepotential change at the anode 333 is applied to the grid 339 causing adecrease of current through its anode, switch 3% and common load Thecharging resistance 2'll and condenser 216 are connected in parallelWith the resistance of the second set of elements of tube '333comprising the anode 3`ii2. Therefore an increase in the resistance ofthe anode 342 circuit will cause a decrease in the charging currentthrough the resistance 217 thereby slightly decreasing the frequency 'ofdeflection.

In operation the horizontal line frequency is adjusted slightly slowerthan the transmitter frequency which will cause the cut off or dischargeof condenser 2% a short interval before theelectron ray arrives at theleaving edge of the screen or picture, which means that the saw toothWave did not reach its peak amplitude. Therefore the glow lamp would beslightly dimmed causing a higher current value through the resistanceZ'i'i. Should the frequency at the receiver become too high the 'glowlamp would develop a greater intensity of light thus reducing thecurrent flow through resistance 221.

From the above description it Will be seen that this regulator Will tendto stabilize the horizontal scanning frequency at the receiver. While Ihave not shown the specific circuits to reg'ulate or stabilize thevertical scanning frequency, I have shown a block diagram 3413 torepresent a similar regulator circuit arrangement comprising a glowlamp, phctocell and double purpose amplifier and it is to be understoodthat this regulator 3543 Will operate to Vautonriatically control orregulate the vertical sweep frequency in a manner similar to thatdescribed above forV horisontal regulation over the Conductors 3413 and3% and through common resistance 345.

The cut ofi devices -or-the offrand on electron relay tube 293 and 3|9may be considered as a safety'device so that the electron ray in tube263 Will continue to oscillate should the signals fade, or thetransmitting station go off the air. With the reception of strongsignals Vthese tubes do not cause thereturn of the electron ray to itsstarting point. However, when monitoring on a transmitter using otherforms of synchronizing signals the voltage on tubes 293 and 319 may beadjusted to return the electron ray in synchronism with the transmitterwithout utilizing any transmitted control signals.

To monitor on a television channel without utilizing at the receiver anyof several different synchronizing or control signals that may betransmitted, assuming that the scanning frequencies are reasonablystable, adjust at 288 and 3|4 the amplitude of the saw tooth Waves orthe sweep of the electron ray to scan a slightly smaller area thannormal and employing the tubes 293 and 359 to develop cut off signals.Then adjust the horizontal and vertical frequencies at 232 and 398 sothat the reproduced picture will have a narrow blackline or border onthe right and bottom edges. This mark is caused by blanking signalsbetween lines and between fields. The black lines at the leaving edgesof the screen Will indicate When the receiver has been adjusted for theproper scanning frequencies as any Mdeviation in the size of thereproduced picture Would show that receiver was operating slow orfast. V

. Referring to Figures 7 and 8, I illustrate two arrangements that maybe utilized in projecting pictures in theatres to two or more Screens.In present day motion picture theatres the pictures are projected toonly one large screen withV the result that the pictures seen by thepatrons close to either wall will 'be very much distorted. To overcomethis distortion I employ three large Screens 378, l''and 389 in VFigure'7 and each served by a separate projecting device as described above inconnection With Figure 5 and as esserne-c 13 t-i'llustrated -by theireference numerals 3'8l, 382 and 383. Since these devices are inmultiple the same pictures will be shown rsimultaneously on the threescreens and the patrons near the sides -of the house will see thepicture as -dis'tinctly as those in -the middle section.

With further reference to Figure '7 I also emrplov-two projectingdevices such as 38V and '382 -for projecting the same pictures to `asingle screen but focused slightlydifferently at the screen; that is,381' may be focused slightly in front of and slightly to one side of theimage projected by the other device 38.2 to give the illusion of depthto the picture.

Figure `8 shows a different arrangement'of large screens 384 and 385 ina theatre so that a greater number of patrons may -view |undistorted-pictures. 'Furthermore many different arrangements of the screens maybe employed to serve larger groups of people; for instance, 'the stagemay be set in the center of an ampitheatre with the pictures showing on:four or six different Screens simultaneously.

In the various circuits shown and described I have simplified thedrawings by indicating the source of potential `by a positive ornegative sign. Also I have omitted the heater filaments :for the varioustubes, but it will be understood that such filaments would -benecessary.

The embodiments of the invention which have `;bee'n given herein areillustrations `of -how the various features may be accomplished and theprinciples involved. It is to be 'understood that the ;inventioncontained herein is capable of em- :bodiment in many other forms andadaptations, :without departing rfrom the spirit of the inven- -tion andthe scope of the appended claims.

'This -invention is a division of applicationsSerial Number 476,897,-filed February 24. 1943.

IHaving thus described my invention, I claim:

`l. -In .a television system, 'a cathode ray :camera tube having ascreen and an electron ray directed at an Vangle toward the screen,means including Vsaw tooth wave generators and an electron tubecontrolled thereby to cause the electron ray to scan lines ofedua'llength onsaid screen, through :a keystone area in a plane at anangle to the surface |of said screen, to produce picture signals, -meansto transmit said signals, a receiver to receive said signals having atleast two cathcde `ray picture ltubes, each of the said picture tubeshavingfan image screen-and an electron beam direct- 1ed toward itsscreen, deflecting nieans including a pair of condensers repeatedl-ychargecl from a source of current to produce saw tooth Waves, `meansunder control of the said saw tooth Waves to cause the electron'beam 'ineach of said picture tubes to scan its associated screen to producethereon images from said picture signals, 'and electrically operablemeans under control of said saw tooth waves to control the -charg'ingycurrent for said condensers to maintain the scanning speed of theelectron beam substantial'ly constant.

2. In a television system, a cathode ray camera tube having an imagescreen and an e'lectron rav directed at an angle toward the screen,means cluding saw tooth wave generators and an electrcn tube control-ledthereby to cause the electron ray to scan lines of equal length on saidscreen to produce picture signals, meansto transmit said signals, areceiver to receive said signals having a cathode ray picture tube, saidpicture tube having an image screen and an electron 'beam directedtoward its screen, defiecting means :including a :pair-of condensersrepeatedlycharged 4'from a source of current to produce saw :toothWaves, means under Vcontrol of said saw tooth waves -to cause theelectron beam to scan the said picture tube screen to producethereonimages from said picture signals, and `electrically operable :meansVunder control of certain of the said saw tooth Waves l'to control thechanging current (for one of said icondensers 'to maintain thehorizontal or vertical sscanning speed of the electron :beamsubstantially constant.

'3. In :a television system, a transmitter, a 'first -cathode raytubeassociated with said'transmitter,

said :tube having an image screen and a first :electronraydirectedtoward the screen, lfirst gen- :erator means :including afirst auxiliary scanning :device to produce line saw tooth Wavesincluding line `synchronizing pulses to control the intervals of theline saw tooth Waves, second generator means including a secondauxil'iary scanning de- 'viice to produce frame saw tooth VWavesincludfing frame :synchronizing pulses to control the intervals of theframe saw tooth waves, means under control :of said line and frame sawtooth Waves vto cause the electron ray 'to Vscan successive frames on:said screen to produce picture :signals representative of a scene, saidfirst scanning .'device havingmeans under control of said framepulseszto produce additional line 'synchronizing pulses for reducing the:interval of theifirst -line saw 'tooth wave in alternate frames tocause the electron ray to scan odd and even vlines on said 'screen in'alternate and intermediate frames respectively, means to transinitsaid-picture signal's and said line and frame syncronizing pulses, areceiver to receive saidpicture signals and said 'line and framesynchronizing pulses, a second cath'o'de -ray tube :associated with saidreceiver, :said 'second tube :having a fluorescent image :screen and a'second e-lectron ray directed toward the fluorescent screen, meansincluding a line saw tooth generator under control of said received linesyncronizing pulses to produce other line saw tooth waves'fzordeflecting the second electron ray forward vand backward horizontally toscan lines on said fluorescent screen, means including a frame saw toothgenerator under control of said received frame synchronizing pulses toproduce other frame saw tooth Waves 'for defiecting the second electronray forward and backward vertically 'to scan successive frames on saidfluorescent screen to produce images thereon from the said receivedpicture signals, saidline saw tooth gener- -ator Ycomprising avcondenser repeatedly charged through an impedance from a source ofcurrent, a first electron tube connected to said impedance, and meansincluding at least `ytwo electron con- -trol tubes respons'ive'toohanges in -amplitude of :sa-id other :line saw tooth Waves tocontrol current 'now through id first 'tube therehy varying chargingcurrent applied to said condenser to maintain the forward horizontalspeed of the second electron 'ray substantially constant.

fi. In a television system., a transmitter, e, first cathode ray tubeassociated with said transmitter, said tube hav-ing an image screen anda first 4electron ray directed toward the screen, first generator meansincluding a first auxilary scanning device to produce line saw toothwaves including line Isyncfhronizing pulses to control the intervals ofthe line saw tooth waves, second igenerator 'means including a secondauxiliary scanning device to produce 'frame saw tooth Waves includingframe synchronizing pulses to control the intervals of the frame sawtooth Waves; means under control of said line and frame saw tooth Wavesto cause the electron ray to scan successive frames on said screen toproduce picture signals representative of a scene, said first scanningdevice having means under control of said frame pulses to produceadditional line synchronizing pulses for reducing the interval of thefirst line saw tooth wave in alternate frames to cause the electron rayto scan odd and even lines on said screen in alternate and intermediateVframes respectively, means to transmit said picture signals and saidline and frame synchronizing pulses, a receiver to receive said picturesignals and said line and frame synchronizing pulses, a pair of cathoderay picture tubes associated with said receiver, each of the saidpicture tubes having a fluorescent image screen and an electron beamdirected toward its associated fiuorescent image screen, means includinga line saw tooth generator under control of said received linesynchronizing pulses to produce other line saw tooth Waves fordeflecting said electron beams forward' and backward horizontally toscan lines on said fluorescent screens, means including a frame sawtooth generator under control of said received frame synchronizingpulses to produce other frame saw tooth Waves for'deflecting the saidelectron beams forward and backward vertically to scan successive framesto produce like-images simultaneously on both of the said fluorescentscreens from the said received picture signals, said line saw toothgenerator comprising a condenser repeatedly charged through an impedancefrom a source of current, a first electron tube connected to saidimpedance, and means-including electron control tubes responsive tochanges in amplitude of said other line saw tooth Waves to vary thecurrent fiowing through said impedance to maintain the forwardhorizontal speed of said'electron beams substantially constant.

5. In a television system, a transmitter, a cathode ray tube associatedWith said transmitter, having an image screen and an electron raydirected toward the screen, line generator means including a firstauxiliary scanning device to produce line saw tooth waves including linesynohronizing pulses to control the intervals of the line saw toothWaves, frame generator means including a second auxiliary scanningdevice to produce frame saw tooth Waves including frame synchronizingsignals to control the intervals of the frame saw tooth Waves, meansunder control of said line and frame saw tooth Waves to cause theelectron ray to scan successive frames on said screen Vto producepicture signals representative of a scene, said first scanning devicehaving means under control of said frame pulses to produce additionalline synchronizing pulses for reducing the interval of the first linesaw tooth wave in alternate frames-to cause the electron ray to scan oddand evenV lines respectively in alternate and intermediate frames onsaid screen;

6; In a television system, a receiver to receive picture signals, linesynchronizing pulses and frame synchronizing pulses, a cathode ray tubeassociated With said receiver, said tube having an image screen and anelectron ray directed toward the screen, means including a line sawtooth generator under control of said received line synchro-nizingpulses to produce line saw tooth wave for deflecting the electron rayforward and backward horizontally to scan lines on said screen, meansincluding a frame saw tooth generator under control 'of' said receivedframe synchronizing pulses to produce frame sawv tooth Waves fordeflecting the electron ray forward and backward vertically to scansuccessive frames o-n said screen to produce images thereon from thesaid received picture signals, said line saw tooth generator comprisinga condenser repeatedly charged through an impedance from a source ofcurrent, a first electron tube connected to said impedance, and meansincluding at least two electron control tubes responsive to changes inamplitude of said line saw tooth waves to control current flowthrough'said first tube thereby varying the current through. said rimpedance to maintain Vthe forward horizontal speed of the electron raysubstantially constant.

7. A television system as claimed in claim 5 wherein the electron'ray isdirected at an angle toward said screen and in addition there isprovided means including an electron tube :under control of said lineand said frame saw'tooth waves to cause the electron ray to scan linesof equal length on said screen.V

8. A television system as claimed in claim 5 and in addition there isprovided a coupling between said second and said first auxiliaryscanning devices to causeV said frame pulses to control the last linesaw tooth Wave for each scanned fra'ne to interlock line and framescanning actions. i V

9. In a television system, means-to receive line synchronizing controlsignals and frame synchronizing controlV signals, a plurality of cathoderay tubes each having an image screen and an electron ray directedtoward its associated image screen, a condenser repeatedly chargedthrough a first impedance from a source of current under control of saidline control signals to produce line saw tooth Waves for defiecting theelectron ray in each of the said tubes forward and back- Wardhorizontally across said Screens, a first electron tube connected tosaid impedance, means including a first pair of. control tubes undercontrol of said line saw tooth Waves to control the current through saidfirst electron tube to in turn control the charging current to saidcondenser for maintaining the forward horizontal speed of the electronray constant, a frame condenser repeatedly charged through a secondimpedance from said source o-f current under control of said framecontrol signals to produce frame saw tooth Waves for deflecting theelectron ray in each of the said cathode ray tubes forward and backwardvertically to scan the said image screens, a second electron tubeconnected to said second'impedance and means including a second pair ofcontrol tubes under control of said said frame saw tooth waves tocontrol the current through said second electron tube to in turn controlthe charging current to said frameV condenser for maintaining theforward vertical speed of the electron ray constant.

10. In a television system, a cathode ray tube having an image screenand an electron ray directed at an angle toward the screen, a fieldsignal cathode ray tube having a field signal screen comprising a fieldphoto-electric tube disposed at one end thereof and coated withfluorescent material With an electron ray capable of impinging thephoto-electric tube to produce spaced field control signals, a linesignal cathode ray tube having a line signal screen comprising a firstline photo-electric tube disposed intermediate the i ends of said linerscreen and a second line photoelectric tube disposed at one endthereof, each 17 of the said photo-electric tubes coated withfiuorescent material and an electron ray capable of impinging said firstand second line photo-electric tubes to produce groups of line controlsignals intermediate said field signals With a difierent intervalbetween the first line signal and a field signal in intermediate groupsthan the interval between the first line signal and a field signal inalternate groups, means under control of said line signals to producehorizontal saw tooth Waves to defiect the electron ray horizontallyacross said mosaic screen, means under control of said field signals toproduce vertical saw tooth Waves to defiect the electron ray verticallyto scan different lines on said mosaic screen in alternate andintermediate fields, and means including an electron tube having atleast two control grids, one grid controlled by said horizontal sawtooth Waves and the other grid controlled by said vertical saw toothWaves to cause the electron ray to scan lines of equal length on saidscreen.

JOHN H. HOMRIGHOUS.

REFERENCES CITED The following references are of record in the file ofthis patent:

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